1. Technical Field
The present invention relates to an auto-balancing device, and to a turntable device and a disk driving device equipped with the auto-balancing device.
2. Description of the Related Art
Recent developments in electronics have led to the use of high-capacity information storage apparatus, such as the CD (compact disc), DVD (digital versatile disc), BD (Blu-ray disc), HD DVD (high definition DVD), etc. Accordingly, there is also a demand for high-speed rotations in the disc drive, which is a device for operating such storage apparatus.
FIG. 1 is a cross-sectional view illustrating an optical disc drive motor according to the related art. Referring to FIG. 1, the motor 10 may be equipped with a turntable device 20. While the motor 10 according to the related art may not provide any problems for rotations at low speeds, but for high speed rotations, the motor 10 may cause serious problems. The centrifugal force applied to a rotating object increases quadratically with respect to the increase in rotation speed. Thus, an increase in the rotation speed of the motor 10 is correlated with an increase in vibration.
The more the rotation speed of the motor 10 is increased, the greater will be the degree of unbalanced centrifugal force, where the resulting vibration may cause difficulty in reading or writing information from or to a disc. Although recent developments in motor-manufacturing techniques have reduced manufacturing tolerances, etc., to increase precision in the products, this is correlated with a rise in manufacturing costs.
FIG. 2 is a cross-sectional view illustrating an optical disc drive motor installed with a turntable device according to the related art. Referring to FIG. 2, a turntable device 30 equipped with an auto-balancing device according to the related art may include multiple correcting balls 32 in a ring-shaped insertion groove. During low-speed rotations, the positions of the correcting balls 32 may be random. After the rotation speed exceeds a certain level, the correcting balls 32 may be distributed evenly across the insertion groove, due to centrifugal forces. In an unbalanced state, the distribution of the correcting balls 32 may be temporarily concentrated in a particular area to resolve this unbalance.
However, at around the resonance point, a phenomenon may occur, in which the correcting balls do not halt within the insertion groove but instead continue to rotate, where this phenomenon is liable to cause problems in operation. Moreover, the correcting balls may act as a dead load in cases where the rotating shaft of the motor forms an angle with the direction of gravity, and problems of noise and vibration may occur during acceleration or deceleration, when the correcting balls collide with one another.